Circuit breaker



D. C. MILLS CIRCUIT BREAKER June 26, 1962 3 Sheets-Sheet 1 Filed June26, 1959 FIG.

INVENTOR. DONALD C. MILLS ATTORNEY D. C. MILLS CIRCUIT BREAKER June26,1962

3 Sheets-Sheet 2 Filed June 26, 1959 INVENTOR. DONALD c. MILLS ATTORNEYJune 26, 1962 D. c. MILLS CIRCUIT BREAKER z Sheets-Sheef 3 Filed June26, 1959 v QE Al.

United States Patent ()filice 3,041,431 Patented June 26, 1962 3,041,431CIRCUIT BREAKER Donald C. Mills, Sunnyvale, Calif., assignor to FederalPacific Electric Company, a corporation of Delaware Filed June 26, 1959,Ser. No. 823,251 9 Claims. (Cl. 200-470) This invention relatesgenerally to a circuit breaker and, more particularly, to a high voltagehigh capacity circuit breaker such as is used in metalclad switchgear.

In the illustrative type circuit breaker, each pole includes two mainconductors that are bridged by a moving contact arm pivotally mountedfor movement between circuit open and circuit closed positions. Themoving contact arm of each pole of this type of circuit breaker iselectrically connected to one of the main conductors of that pole andmoves into and out of substantially normal contact engagement with acompanion contact carried by the other main conductor of that pole. Eachmoving contact arm is electrically connected to one of its mainconductors at all times and throughout its pivotal movement.

The primary aim and object of the present invention is the provision ofan improved arrangement for both pro viding mechanical support for thecontact arm and for electrically connecting one of the main conductorsof each pole to the associated movable contact arm. A related objectresides in the provision of a novel pivotal support and electricalconnection for such a pivoted contact arm which avoids the need forconnecting braid. A more particular object of the present inventionresides in the provision of an improved arrangement for electricallyconnecting a main conductor to a companion movable contact arm asaforedescribed in which the elect1ical connection is made through apivotal connection at the pivotal mounting of the movable contact unit,this arrangement providing a reliable electrical connection from suchconductor to the contact arm during the range of pivotal movementthereof.

Yet another object of the present invention is the provision of agenerally improved circuit breaker of the aforenoted character which iseminently suitable for the accomplishment of its intended purposes.

The illustrative embodiments of the invention, which have been generallyreferred to above as incorporating the various novel features of theinvention, is more fully described in the remainder of thisspecification, from which further novel features and objects andadvantages will become apparent. In the following description referenceis made to the accompanying drawings forming part of this disclosure. Inthe drawings:

FIGURE 1 is a side elevation, with parts broken away, of an illustrativecircuit breaker embodying the present invention in both detailed formsshown in the remaining figures;

FIGURE 1A is a vertical section as viewed from the line 1A1A in FIGURE2, showing a part of the circuit breaker of FIGURE 1 embodying thefeatures of the present invention;

FIGURE 2 is a plan sectional view taken on the line 22 of FIGURE 1A;

FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 1A; 7

FIGURE 4 is a view similar to FIGURE 1A showing another embodiment ofthe present invention; and

FIGURE 5 is a plan sectional view taken on the line 5-5 of FIGURE 4.

Referring to the drawings, and more particularly to FIGURE 1A, there isshown a part of circuit breaker which is of the same general type shownand described in my application Serial No. 684,268, filed September 16,1957, for Circuit Breakers, now Patent No. 2,943,168,

, June 28, 1960, and assigned to the assignee herein, refershaft.

ence being made to said application for a more detailed description ofthe circuit breaker. Each pole of the circuit breaker 10 includes studs11 and 12, these studs also being referred to herein as main orstationary conductors. These studs are bridged by the moving contact arm14 which is pivotally mounted in the manner to be described in detailbelow. The circuit breaker has three poles, and accordingly there arethree pairs of main conductors and three contact arms 14, the latterbeing pivotally movable between circuit open and circuit closedpositions. Each contact arm 14 is pivotally mounted on its ownsupporting shaft 44 (98) of steel or the like carried in boards orplates 46 of insulation that flank each pole. (The numbers inparentheses refer to parts in FIGURES 4 and 5 whereas the other numbersrefer to parts in FIG- URES 1A, 2 and 3.)

The common operating mechanism for all of the moving contact arms 14includes a casting 14a that extends across all of the poles. Thiscasting is carried in arms 14b that are suitably pivoted at 14c. Casting14a has arms 14d connected to push rods 14c of insulation there beingone push rod for each moving contact arm 14. A solenoid 14 providesdriving power for operating casting 14a to drive and retain contact arms14 to the closed position illustrated, acting through a trip-freerelease coupling 14g. The details of this mechanism are more fully shownand described in my application mentioned above and are omitted hereinasmuch as they are apparently not essential to an understanding of thepresent invention.

It will be understood that in closing the circuit breaker and keeping itclosed, a powerful upward force is directed along rod 14c, this forceacting about shaft 44 for operating contact arm 14 and for maintainingcontact pressure of companion contacts 14h against each other.conventionally suitable spring biasing means is incorporated in thecontact structure. Reaction force is'provided by insulation plates 46(92) fastened to base 101: and to stud 11 or to both studs 11 and 12 asmay be preferred. Plates 46 (92) carry supporting shafts 44 (90). Anadditional ventical rod of insulation (not shown) is added to each polewhen required for increased strength, having its lower end fixed to aportion of base 10a and at its upper end having a hole tightly receivingshaft 44 (90) or the hub of contact arm 14 midway between boards 46 (92)of each pole. Shaft 44 (90) provides mechanical pivotal support for themoving contact arm 14, providing a pivotal axis at right angles to stud12.

.Electrical connection from conductor or stud 12 to pivotal movingcontact arm 14 is provided separate and independent of the mechanicalpivotal support without resort tobraid, in a manner to establish anexcellent elec trical connection despite inevitable mechanicalvariations in the relationship between the location of stud 12 and thepivotal axis of the contact arm. Such variations occur in production asa result of manufacturing tolerance, and variations also occur in usedue to wear, mechanical stresses and other causes.

Referring now to FIGS. 1A, 2 and 3, conductor 12 is tubular and ofcircular cross section and is mounted within a complementary insulatingsleeve 16. Conductor 12 has a conductor stub 18 suitably securedthereto; Stub 18 has a terminal fitting 20 in the form of a solidcircular stub peripheral recess of sleeve 16. The clamp ring is forced Iinto engagement with bushing 26 by the bushing flange 30, by tightenedclamping bolts 32 The assembly of parts 12, 16 and 18 is supported;

extending through suitable openings of said flange and received inthreaded companion apertures 34 of the back plate. Thus the fitting 20is electrically connected to conductor 12. The stub 18 is provided witha peripheral recess 36 and the inner end of the conductor 12 is seatedand secured therein, as by brazing.

The contact arm 14 comprises a pair of laterally spaced operating arms3-8 having conductive blades 40 as of copper secured thereto, said armsand blades being united to bushings or the like constituting aconductive hub 42. The unitary contact arm 14, including parts 38, 40and 42, is a rigidly interconnected assembly, preferably brazed and thehub 42 is pivotally mounted on the stationary shaft 44 carried by theinsulator plates 46. Thus the contact arm 14 is movable about thepivotal axis established by shaft 44 between circuit open and circuitclosed positions. Y

A contact assembly, generally'de'signated 48, is interposed betweenterminal fitting 20 and hub 42 for electrically connecting the conductor12 to pivotal contact arm 14. The contact assembly 48 comprises acompanion pair of U-shaped bridging contact members 50 which are springbiased towards each other in the manner to be described in detailhereinafter, each member 50 comprising a part 52 at'the base of the Uand having a pair of laterally spaced legs 54. Base part 52 engagesterminal fitting 20 and legs 54 engage hub 42, the members 50 therebybridging conductor 12 and contact arm 14. More particularly, the basepart 52 is cut away as indicated at 56 to define the oppositely inclinedpair of surfaces 58 which mutually diverge '(FIG. 3) to receive fitting20 and slant approximately 45 degrees to the horizontal. Surfaces 58'have two silver-tungsten contacts 60 secured thereon for correspondingelectrical contact with the peripheral surface of fitting 20. Each leg54 is similarly provided with a cutaway area 62 having similarly slantedsurfaces 64 provided with s'ilver tungsten contacts 66, the latterengaging the peripheral surface of hub 42 to provide a pair ofconducting paths from each leg to the hub 42. From the above it will beapparent that two current paths are provided from fitting'20 to eachmember 50 and that four current paths are provided from the hub to eachof the u shaped members. Where hub 42 is engaged by contacts 66, it isadvantageously provided with a sleeve of silver, united to the body ofthe hub, for low-resistance contact.

The members 50 are spring biased towards each other, for pressureengagement both with fittings 20 and with hub 42. The axis 68 of thespring bias is disposed substantially closer to fitting 20 than to saidhub, approximat'ely at a distance of one-third the distance between basepart 52 and the axis of the hub. This off-center positioning ofthe'biasing axis provides higher contact pressure between contacts 60'and fitting 20 than the pressure between contacts 66 and the hub 42.This increased'contact pressure is provided to reduce the contactresistance at the position of the lesser number of current paths.

A flat plate 70 bridges legs 54 of upper member and a U-shaped plate 72bridges legs 54 of lower member 50, said plate 72 having a base wall 74spaced from plate 70. A fiat plate 76 is spaced below plate 72 and acoiled compression spring 73 is disposed between wall 74 and plate 76 toprovide the requisite and 76' are maintained is assembled relation bythe bolts 78 and nuts 80 as shown. Thus the major portion of the biasingforce-exerted by spring 73 is applied between con-.

tacts 60 and fitting 20, the current flowing through each of the fourcontacts 60'splitting into a pair of current paths at the eight contacts66.

1 Upon pivotal movement of the moving contact arm 14, the hub 42 rotateswith respect to the members 50 and high current conduction through saidmembers 50' to the hub is maintained for the full range ofpivotalmovement. All of the contacts are biased into engagement with acompanion cylindrical contact surface and due to the inbiasing force;Plates 70, 72'

clined engagement of the contacts with their companion surfaces a forcemultiplication is provided to thereby increase the biasing force exertedat such contacting areas. The downward component of biasing force isapplied to the cylindrical contacting surfaces through contacts disposedon an inclined plane thereby substantially increasing the contactpressure at such contacts. From the above, it will be apparent that thecontact pressure at contacts 60 is substantially greater than thecontact pressure at contacts 66 to compensate for the greater currentflow through contacts 60.

The members 50 are self-centering in two directions, that is in adirection along the length of the legs 54 and in a direction along thelength of base parts 52. The members 50 compensate for a large latitudeof variation in the relative positioning of fitting 20 and the hub 42.Under short-circuit or fault-current conditions a powerfulelectrodynarnic attraction force is set up between the members 50,supplementing the contact pressure applied by spring 73, to therebyinsure requisite contact pressure during severe current conditions.

The electrodynamic force of attraction results from the currents carriedin the same direction by each leg of the upper U and the opposed leg ofthe lower U. The contact pressure of the spring 110 is greatly augmentedelectrodynamically during short-circuit current peaks and thisaccommodates dimensional variations in the relative orientation of stud20 and contact hub 42 of contact arm 14 on pivotal shaft 44 throughoutthe pivotal stroke of the moving contact arm.

With reference to FIGS. 4 and 5, there is shown another embodiment ofsome of the features of the present invention as represented in theabovedescribed embodiment. The form of bridging contact assembly isspecifically diiferent in FIGS. 4 and 5. This specific construction inthese figures is an embodiment of certain features of my invention asshown in FIGS. 1A, 2. and 3, the form in FIGS. 4 and 5 being presentlypreferred in that it provides twice the number of bridging contactmembers and a larger number of contacts, for higher current carryingcapacity. Although this embodiment is disclosed as a preferred form ofcertain features of my invention, the details thereof form no part of myinvention to the extent that they depart from that in FIGS. 1A, 2 and 3.

Contact assembly 48' in FIGS. 4 and 5 comprises cornpanion pairs ofupper and lower plate-like contact members 82 and 82, respectively,there being a total of eight contact members interconnecting the contactarm 14' and conductor 12'. Conductor 12 is provided with a terminalfitting 20' of rectangular configuration having opposite planar contactsurfaces 84. Contact arm 14' comprises contact blades or plates 86 and86', the latter serving not only as conductors but also mechanically inthe manner of plates 38 of FIGS. 1A, 2 and 3, for mechanical connectionto push rods 142 (FIG. '1). Contact bushings 88 are rigidly joined toplates 86 and 86 as by brazing for pivotal movement and the plates areelsewhere conductively rigidly united as a single unitary contact arm.The bushings 88 are coaxially disposed at the lower end of the contactarm 14' and are pivotally mounted on the stationary shaft90 which iscarried and located by the spaced plates 92 corresponding to the plates46 in the other embodiment described. Each contact'member 82, 82'bridges one of the surfaces 84 and a companion bushing 88. p a

Each contact member 82, 82' is provided with an arcuate contact 94 ofsuitable low contact-resistance material at one end and the other end(like legs 54 of the previous embodiment) is provided with a cutawayarea 96 having surfaces 98 inclined approximately 45 degrees to thehorizontal and provided with contacts 100 as of silvertungsten. Thesecontacts engage the cylindrical surface of a companion bushing 88 toprovide a pair of conducting paths from the contact'member 82 to thebushing. Thus a single current path is provided from fitting 20 to eachcontact member 82 at contact 94 and two current paths are provided fromthe contact member to the associated bushing.

The upper and lower contact members are biased toward each other alongbiasing axis 68 and into engagement with fitting 2t) and with thebushings. The biasing axis is disposed substantially closer to fitting20' than to the bushings, substantially closer than and approximately ata point one-third of the distance between contact 94 and the axis ofbushings 88, to provide for greater biasing force at each contact 94where a single current path is provided than at contacts 88 each ofwhich carries only half the current of contact 94, in the same manner asin the previous embodiment. Here, too, the slant angle of each contact88 relative to the direction of force application tends to increase thepressure at each contact 88' as compared to what it would be in the caseof unslanted, normal contact engagement at 94. A companion pair of uppercontact members and a companion pair of lower contact members haveassociated therewith upper and lower plates 102 and 104, respectively,seated in suitable recesses provided therefor in said contact members,said plates being suitably apertured therethrough to receive the bolt106, the head of which is provided with a pin 108 which is in engagementwith the upper plate. A coil spring 110 is carried by the lower end ofbolt 106, spring 110 being compressed between plate 104 and washer 112which is held in place by locknuts 114. Thus the spring 110 applies aforce to bias its associated four contact members into engagement withfittings 20' and bushings 88, like spring 73 that biases the four legsof the two U- shaped members into similar pressure contact.

The major portion of the biasing force exerted by springs 110 is appliedbetween contacts 94 and fitting 20' for minimum contact resistance. Thecurrent flowing through each contact 94 splits into a pair of currentpaths at the pair of contacts 100 of each bridging contact memher. As inthe case of the previous embodiment, the downward component of biasingforce is applied to the contacting surfaces of the bushings throughcontacts 100 disposed on an inclined plane thereby substantiallyincreasing the contact pressure at such contacts. The contact membersare self-centering on the bushings and compensate for a large latitudeof irregularities and dimensional variations between the fitting 20' andthe bushings. The centering of the contacts 100 on the bushingsdetermines the location of the contact 94 with respect to the fitting20. Under short-circuit or fault-current conditions, a powerfulelectrodynamic attraction force is set up between the opposed upper andlower bridging contact members, supplementing the spring-biased contactpressure.

Various additional modifications of the above embodiments of theinvention will readily occur to those skilled in the art, and thereforethe invention should be broadly construed in accordance with its fullspirit and scope.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. A circuit breaker having a companion pair of contacts, a firststationary conductor carrying one of said contacts, a second stationaryconductor, a contact arm movable pivotally about an axis and carryingthe other of said contacts, a contact hub disposed concentrically aboutsaid axis and forming a unitary portion of said contact arm, aprojecting portion extending from said second conductor substantiallyperpendicularly toward said contact hub, mutually opposed bridgingcontact elements having spring biasing means and embracing saidprojecting portion and said contact hub and slidably engaging saidprojecting portion, and means providing pivotal support for said contactarm constraining the contact thereof to move about a fixed axis into andout of substantially normal contact with said one of said contacts.

2. A circuit breaker having a companion pair of contacts, a firststationary conductor carrying one of said contacts, a contact armcarrying the other of said contacts, and a second stationary conductor,means pivotally supporting said contact arm and constraining the contactthereof to move about an axis into and out of substantially normalcontact with said one of said contacts, and additional meanselectrically connecting said contact arm to said second stationaryconductor, said connecting means including a contact hub disposedconcentrically about said axis and forming a unitary part of saidcontact arm, a projecting portion on said second conductor extendingsubstantially perpendicularly toward said contact hub, and spring-biasedmutually opposed bridging contact elements embracing said projectingportion and said contact hub and slidably engaging said projectingportion.

3. A circuit breaker having a companion pair of contacts, a firststationary conductor carrying one of said contacts, a contact armcarrying the other of said contacts, and a stationary conductor, meanspivotally supporting said contact arm and constraining the contactthereof to move about an axis into and out of substantially normalcontact with said one of said contacts, and additional meanselectrically connecting said contact arm to said second stationaryconductor, said connecting means including a contact hub disposedconcentrically about said axis and forming a unitary part of saidcontact arm, a projecting portion on said second conductor extendingsubstantially perpendicularly toward said contact hub and saidprojecting portion, said contact assembly including plural opposed pairsof generally fiat elongated bridging contact elements disposed incoplanar edgewise opposition, each said element adjacent one end thereofslidably engaging a lateral surface of said projecting portion of saidsecond conductor and each said bridging contact element adjacent theopposite end thereof having divergent longitudinally spaced contacts inengagement with said contact hub.

4. A circuit breaker having a companion pair of contacts, a firststationary conductor carrying one of said contacts, a contact armcarrying the other of said contacts, and a stationary conductor, meanspivotally supporting said contact arm and constraining the contactthereof to move about an axis into and out of substantially normalcontact with said one of said contacts, and additional meanselectrically connecting said contact arm to said second stationaryconductor, said connecting means including a contact hub disposedconcentrically about said axis and forming a unitary part of saidcontact arm,

a projecting portion on said second conductor extending substantiallyperpendicularly toward said contact hub, and a bridging contact assemblyinterconnecting said contact hub and said projecting portion, saidcontact assembly including plural opposed pairs of generally flatelongated bridging contact portions disposed in coplanar edgewiseopposition, each said bridging portion extending into slidableengagement with a lateral surface of said projecting portion of saidsecond conductor and each said bridging contact portion also havingdivergent longitudinally spaced contacts in engagement with said contacthub, said contact assembly including spring biasing means disposed toact against said elongated bridging contact portions at a locationbetween the ends thereof but closer to said projecting portion than tosaid hub.

5. A circuit breaker having a companion pair of contacts, a firststationary conductor carrying one of said contacts, a contact armcarrying the other of said contacts, and a stationary conductor, meanspivotally supporting said contact arm and constraining the contactthereof to move about an axis into and out of substantially normalcontact with said one of said contacts and additional means electricallyconnecting said cont-act arm to said second stationary conductor, saidconnecting means including contact hub disposed concentrically aboutsaid axis and forming a unitary part of said contact arm, a projectingportion on said second conductor extending toward said contact hub, anda bridging contact assembly interconnecting said contact hub and saidprojecting portion, said bridging contact assembly including a group offour elongated bridging contact portions, each bridging contact portionhaving longitudinally spaced divergent contact portions adjacent one endthereof engaging said contact hub, and each bridging contact portionextending to a point of contact with a lateral surface of saidprojecting portion, said bridging contact portions being disposed aslaterally adjacent pairs of confronting elements embracing said contacthub and said projecting portion, and a common spring biasing unit actingon all four of said elongated bridging contact portions for establishingbias at each point of contact and thereby centering said divergentcontact portions about said contact hub.

6. A circuit breaker having a companion pair of contacts, a firststationary conductor carrying one of said contacts, a conducting armcarrying the other of said contacts, and a stationary conductor, meanspivotally supporting said contact arm and constraining the contactthereof to move about an axis into and out of substantially normalcontact With said one of said contacts, and additional meanselectrically connecting said contact arm to said second stationaryconductor, said connecting means including contact hub disposedconcentrically about said axis and forming a unitary part of saidcontact arm, a projecting portion on said second conductor extendingtoward said contact hub, and a bridging contact assembly interconnectingsaid contact hub and said projecting portion, said bridging contactassembly including a group of four elongated bridging contact portions,each bridging contact portion having longitudinally spaced divergentcontact portions adjacent one end thereof engaging said contact hub, andeach bridging contact portion extending into contact with a lateralsurface of said projecting portion, said bridging contact portions beingdisposed as laterally adjacent pairs of confronting elements embracingsaid contact hub and said projecting element, and a common springbiasing unit acting on all four of said elongated bridging portions forestablishing bias at each point of contact and thereby centering saiddivergent contact portions about said contact hub, pairs of saidbridging contact portions being integral with each other and of U-shapedconfiguration, so as to constitute two confronting U-shaped bridgingcontact members, embracing said contact hub and said projecting portion,

the latter having a cylindrical lateral surface, and the base of eachU-shaped member having divergent contact portions engaging saidcylindrical lateral surface.

7. A circuit breaker, comprising a stationary conductor having aprojecting cylindrical portion, a movable contact arm and a shaftpivotaily supporting said arm for movement between circuit open andcircuit closed positions and having a hub provided with a cylin- 50drical contact surface a'nd a bridging contact assembly for electricallyconnecting said blade and hub to thereby electrically connect saidconductor and contact unit for the range of pivotal movement thereof,said assembly comprising a pair of U-shaped contact members embracingsaid cylindrical projecting portion and said hub, each of said contactmembers comprising a base part having divergent contacts in contactingengagement with the cylindrical projecting portion of said blade andlaterally spaced legs having divergent contacts spaced apart along therespective legs and in contacting engagement with said hub, and meansfor biasing said contact members toward each other, said contact membershaving an eiectrodynamic attraction force set up therebetween undershort circuit conditions to supplement the contact pressure of saidbiasing means.

8. A circuit breaker, comprising first and second stationary generallyparallel terminal conductors, said first terminal having a projectingend portion, a movable contact arm, and a shaft pivotally supportingsaid arm for movement between circuit open and circuit closed positions,a'companion contact on said second conductor engageable by said contactarm in the closed position, said arm having a hub provided with acylindrical contact surface, and a bridging contact assembly forelectrically connecting said projecting portion and hub to therebyelectrically connect said conductor and contact arm for the range ofpivotal movement thereof, said'assembly comprising a pair ofsubstantially U-shaped members aligned in edge to edge facing relation,the opposed edges of the base portions thereof formed to receive saidprojecting portion therebetween, the opposed edges of each pair of legsbeing formed to receive said hub therebetween, and means biasing saidU-shaped members toward each other.

9. A circuit breaker, comprising first and second stationary elongatedgenerally parallel terminal conductors, a movable contact arm, and ashaft pivotally supporting said arm for rotation about an axis spacedfrom the end and transverse to said first conductor between circuit openand circuit closed positions, a companion contact on said secondconductor engageable by said contact arm in the closed position, saidarm having a hub provided with a cylindrical contact surface, aplurality of elongated conductive bridging elements for electricallyconnecting said stationary conductor and hub to thereby electricallyconnect said conductor and contact arm for the range of pivotal movementthereof, said bridging elements being arranged in opposed pairs exposedto each other and spanning said space between the conductor and the hub,and spring biasing means urging the opposed bridging elements of eachpair toward each other and into contact with said hub and saidconductor, said bridging elements slidably' engaging said conductor.

References Cited in the file of this patent UNITED STATES PATENTS YoungOct. 9, 1932 2,376,818 Rubel May 22, 1945 2,707,732 Ortwig May 3, 1955

